The present invention relates generally to alloys and metallic compositions more specifically the invention pertains to materials which will not expand during oxidation or nitridation and which, therefore are useful in the manufacture of semiconductor devices, electrical circuits, and optical elements.
Thin films for various semiconductor and optical uses have been formed upon a substrate for support. In the past, attempts have been made to create patterned aluminum films by oxidizing the portion of a film which was not to be aluminum, that is, selective oxidation of a film. The increase in volume in the oxidation process caused high stresses to be induced with resulting delamination which makes the product unusable.
The task of providing thin insulator films which are stress free is alleviated, to some extent by the systems disclosed in the following U.S. Patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 1,224,362 issued to Cooper; PA1 U.S. Pat. No. 2,018,143 issued to McCarty et al; PA1 U.S. Pat. No. 2,066,912 issued to Ruben; PA1 U.S. Pat. No. 2,087,269 issued to Stroup; PA1 U.S. Pat. No. 2,190,290 issued to Kirsebom; PA1 U.S. Pat. No. 3,551,143 issued to Marukawa et al; PA1 U.S. Pat. No. 3,825,442 issued to Moore; PA1 U.S. Pat. No. 3,839,084 issued to Cho et al; PA1 U.S. Pat. No. 3,856,647 issued to Blachman; PA1 U.S. Pat. No. 3,949,275 issued to Muenz; PA1 U.S. Pat. No. 3,962,485 issued to Anderson et al; PA1 U.S. Pat. No. 3,997,339 issued to Fickelscher; PA1 U.S. Pat. No. 4,731,132 issued to Alexander; PA1 U.S. Pat. No. 4,056,457 issued to Vossen, Jr., and PA1 U.S. Pat. No. 4,851,192 issued to Baba et al.
Blachman discloses multi-layer control of stress in thin films wherein molybdenum, when sputtered directly onto a substrate to which a controlled dc voltage was applied, could be laid down with low stress but relatively high resistivity. When a second layer of molybdenum is sputtered on the first layer at a different voltage, a thin film could be obtained having low stress as well as low resistivity.
Anderson et al disclose a method for forming uniform stress-free thin films of metals, semiconductors and insulators. A molybdenum grid-tantalum structure is prepared, and a collodion film is settled on the grid to form a flat surface upon which a film could be deposited such as an amorphous germanium film. Other materials are suggested but not disclosed.
Vossen, Jr. discloses a method of depositing low stress hafnium thin films by radio frequency sputtering the films on alumina or sapphire substrate at high deposition rates.
Moore discloses a method whereby film cracking is prevented by formation of a glass layer over a first layer having abrupt surface contours. The glass is heated sufficiently for plastic flow to around the edges and avoid cracking.
While the above-cited references are instructive, the task of providing stress free insulators represents an ongoing technological need. The present invention is intended to help satisfy that need.